/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/pthread/pthread_mutexunlock.c
 *
 *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
#include <debug.h>

#include "pthread/pthread.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_mutex_unlock
 *
 * Description:
 *   The pthread_mutex_unlock() function releases the mutex object referenced
 *   by mutex. The manner in which a mutex is released is dependent upon the
 *   mutex's type attribute. If there are threads blocked on the mutex object
 *   referenced by mutex when pthread_mutex_unlock() is called, resulting in
 *   the mutex becoming available, the scheduling policy is used to determine
 *   which thread shall acquire the mutex. (In the case of PTHREAD_MUTEX_RECURSIVE
 *   mutexes, the mutex becomes available when the count reaches zero and the
 *   calling thread no longer has any locks on this mutex).
 *
 *   If a signal is delivered to a thread waiting for a mutex, upon return from
 *   the signal handler the thread resumes waiting for the mutex as if it was
 *   not interrupted.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

int pthread_mutex_unlock(FAR pthread_mutex_t *mutex)
{
	int ret = EINVAL;

	svdbg("mutex=0x%p\n", mutex);
	DEBUGASSERT(mutex != NULL);

	/* Make sure the semaphore is stable while we make the following checks.
	 * This all needs to be one atomic action.
	 */
	sched_lock();
	if (mutex != NULL) {
#if !defined(CONFIG_PTHREAD_MUTEX_UNSAFE) || defined(CONFIG_PTHREAD_MUTEX_TYPES)
		/* Does the calling thread own the semaphore?  If no, should we return
		 * an error?
		 *
		 * Error checking is always performed for ERRORCHECK and RECURSIVE
		 * mutex types.  Error checking is only performed for NORMAL (or
		 * DEFAULT) mutex type if the NORMAL mutex is robust.  That is either:
		 *
		 *   1. CONFIG_PTHREAD_MUTEX_ROBUST is defined, or
		 *   2. CONFIG_PTHREAD_MUTEX_BOTH is defined and the robust flag is set
		 */

#if defined(CONFIG_PTHREAD_MUTEX_ROBUST)
		/* Not that error checking is always performed if the configuration has
		 * CONFIG_PTHREAD_MUTEX_ROBUST defined.  Just check if the calling
		 * thread owns the semaphore.
		 */

		if (mutex->pid != (int)getpid())
#elif defined(CONFIG_PTHREAD_MUTEX_UNSAFE) && defined(CONFIG_PTHREAD_MUTEX_TYPES)
		/* If mutex types are not supported, then all mutexes are NORMAL (or
		 * DEFAULT).  Error checking should never be performed for the
		 * non-robust NORMAL mutex type.
		 */
		if (mutex->type != PTHREAD_MUTEX_NORMAL && mutex->pid != (int)getpid())
#else							/* CONFIG_PTHREAD_MUTEX_BOTH */
		/* Skip the error check if this is a non-robust NORMAL mutex */

		bool errcheck = ((mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0);
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
		errcheck |= (mutex->type != PTHREAD_MUTEX_NORMAL);
#endif

		/* Does the calling thread own the semaphore?  If not should we report
		 * the EPERM error?
		 */

		if (errcheck && mutex->pid != (int)getpid())
#endif
		{
			/* No... return an error (default behavior is like PTHREAD_MUTEX_ERRORCHECK) */

			sdbg("Holder=%d returning EPERM\n", mutex->pid);
			ret = EPERM;
		} else
#endif							/* !CONFIG_PTHREAD_MUTEX_UNSAFE || CONFIG_PTHREAD_MUTEX_TYPES */

#ifdef CONFIG_PTHREAD_MUTEX_TYPES
			/* Yes, the caller owns the semaphore.. Is this a recursive mutex? */

			if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->nlocks > 1) {
				/* This is a recursive mutex and we there are multiple locks held. Retain
				 * the mutex lock, just decrement the count of locks held, and return
				 * success.
				 */
				mutex->nlocks--;
				ret = OK;
			} else
#endif							/* CONFIG_PTHREAD_MUTEX_TYPES */

				/* This is either a non-recursive mutex or is the outermost unlock of
				 * a recursive mutex.
				 *
				 * In the case where the calling thread is NOT the holder of the thread,
				 * the behavior is undefined per POSIX.  Here we do the same as GLIBC:
				 * We allow the other thread to release the mutex even though it does
				 * not own it.
				 */

			{
				/* Nullify the pid and lock count then post the semaphore */

				mutex->pid = -1;
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
				mutex->nlocks = 0;
#endif
				ret = pthread_mutex_give(mutex);
			}
	}

	sched_unlock();
	svdbg("Returning %d\n", ret);
	return ret;
}
